6 files changed, 16 insertions, 12 deletions
diff --git a/guides/source/active_job_basics.md b/guides/source/active_job_basics.md
index 39239852ca..0ebef46373 100644
--- a/guides/source/active_job_basics.md
+++ b/guides/source/active_job_basics.md
@@ -165,6 +165,7 @@ Here is a noncomprehensive list of documentation:
 - [Sneakers](https://github.com/jondot/sneakers/wiki/How-To:-Rails-Background-Jobs-with-ActiveJob)
 - [Sucker Punch](https://github.com/brandonhilkert/sucker_punch#active-job)
 - [Queue Classic](https://github.com/QueueClassic/queue_classic#active-job)
+- [Delayed Job](https://github.com/collectiveidea/delayed_job#active-job)
 
 Queues
 ------
diff --git a/guides/source/active_record_basics.md b/guides/source/active_record_basics.md
index b9e24099b1..a67e2924d7 100644
--- a/guides/source/active_record_basics.md
+++ b/guides/source/active_record_basics.md
@@ -202,6 +202,8 @@ class Product < ApplicationRecord
 end
 ```
 
+NOTE: Active Record does not support using non-primary key columns named `id`.
+
 CRUD: Reading and Writing Data
 ------------------------------
 
diff --git a/guides/source/active_record_querying.md b/guides/source/active_record_querying.md
index 02055e59f0..fd1dcf22c0 100644
--- a/guides/source/active_record_querying.md
+++ b/guides/source/active_record_querying.md
@@ -1267,7 +1267,7 @@ This is because it is ambiguous whether they should appear on the parent record,
 Scopes
 ------
 
-Scoping allows you to specify commonly-used queries which can be referenced as method calls on the association objects or models. With these scopes, you can use every method previously covered such as `where`, `joins` and `includes`. All scope methods will return an `ActiveRecord::Relation` object which will allow for further methods (such as other scopes) to be called on it.
+Scoping allows you to specify commonly-used queries which can be referenced as method calls on the association objects or models. With these scopes, you can use every method previously covered such as `where`, `joins` and `includes`. All scope bodies should return an `ActiveRecord::Relation` or `nil` to allow for further methods (such as other scopes) to be called on it.
 
 To define a simple scope, we use the `scope` method inside the class, passing the query that we'd like to run when this scope is called:
 
diff --git a/guides/source/active_storage_overview.md b/guides/source/active_storage_overview.md
index d5387219f5..65d4e2934f 100644
--- a/guides/source/active_storage_overview.md
+++ b/guides/source/active_storage_overview.md
@@ -635,7 +635,7 @@ input.addEventListener('change', (event) => {
   input.value = null
 })
 
-const uploadFile = (file) {
+const uploadFile = (file) => {
   // your form needs the file_field direct_upload: true, which
   //  provides data-direct-upload-url
   const url = input.dataset.directUploadUrl
diff --git a/guides/source/routing.md b/guides/source/routing.md
index 84de727c11..0a0f1b6754 100644
--- a/guides/source/routing.md
+++ b/guides/source/routing.md
@@ -543,6 +543,8 @@ resources :photos do
 end
 ```
 
+NOTE: If you're defining additional resource routes with a symbol as the first positional argument, be mindful that it is not equivalent to using a string. Symbols infer controller actions while strings infer paths.
+
 #### Adding Routes for Additional New Actions
 
 To add an alternate new action using the `:on` shortcut:
diff --git a/guides/source/testing.md b/guides/source/testing.md
index f0a1a8a3f0..02b60a395b 100644
--- a/guides/source/testing.md
+++ b/guides/source/testing.md
@@ -474,12 +474,11 @@ takes your entire test suite to run.
 
 The default parallelization method is to fork processes using Ruby's DRb system. The processes
 are forked based on the number of workers provided. The default is 2, but can be changed by the
-number passed to the parallelize method. Active Record automatically handles creating and
-migrating a new database for each worker to use.
+number passed to the parallelize method.
 
 To enable parallelization add the following to your `test_helper.rb`:
 
-```
+```ruby
 class ActiveSupport::TestCase
   parallelize(workers: 2)
 end
@@ -489,32 +488,32 @@ The number of workers passed is the number of times the process will be forked.
 parallelize your local test suite differently from your CI, so an environment variable is provided
 to be able to easily change the number of workers a test run should use:
 
-```
+```bash
 PARALLEL_WORKERS=15 rails test
 ```
 
-When parallelizing tests, Active Record automatically handles creating and migrating a database for each
+When parallelizing tests, Active Record automatically handles creating a database and loading the schema into the database for each
 process. The databases will be suffixed with the number corresponding to the worker. For example, if you
 have 2 workers the tests will create `test-database-0` and `test-database-1` respectively.
 
 If the number of workers passed is 1 or fewer the processes will not be forked and the tests will not
 be parallelized and the tests will use the original `test-database` database.
 
-Two hooks are provided, one runs when the process is forked, and one runs before the processes are closed.
+Two hooks are provided, one runs when the process is forked, and one runs before the forked process is closed.
 These can be useful if your app uses multiple databases or perform other tasks that depend on the number of
 workers.
 
 The `parallelize_setup` method is called right after the processes are forked. The `parallelize_teardown` method
 is called right before the processes are closed.
 
-```
+```ruby
 class ActiveSupport::TestCase
   parallelize_setup do |worker|
     # setup databases
   end
 
   parallelize_teardown do |worker|
-    # cleanup database
+    # cleanup databases
   end
 
   parallelize(workers: 2)
@@ -530,7 +529,7 @@ parallelizer is backed by Minitest's `Parallel::Executor`.
 
 To change the parallelization method to use threads over forks put the following in your `test_helper.rb`
 
-```
+```ruby
 class ActiveSupport::TestCase
   parallelize(workers: 2, with: :threads)
 end
@@ -542,7 +541,7 @@ The number of workers passed to `parallelize` determines the number of threads t
 want to parallelize your local test suite differently from your CI, so an environment variable is provided
 to be able to easily change the number of workers a test run should use:
 
-```
+```bash
 PARALLEL_WORKERS=15 rails test
 ```